There are numerous products that are known to contain polyglucosidic units which we shall call "polyglucose" or "polyglucoses" hereinafter, for instance cellulose.
Cellulose has the following general formula (C.sub.6 H.sub.10 O.sub.6).sub.n and may be represented as: ##STR1##
On the basis of conformational analysis, a better structural presentation is probably given by formula (2). ##STR2## Where n is of the order of for instance 300 to 500, and possibilities exist that the beta 1,4-linkage may be other than the glucosidic bonds, but to a minor extent.
Dextrins have the general formula (C.sub.6 H.sub.10 O.sub.5)n.times.H.sub.2 O are for instance obtained by controlled hydrolysis of starch and may also be represented by the formulation shown at (3). In the case of cylic dextrins, also called cyclodextrins: ##STR3##
Cyclodextrins may also be represented by the following formula: ##STR4## where for alpha-cyclodextrin n is 6,
for beta-cyclodextrin n is 7, and PA1 for gamma cyclodextrin n is 8 PA1 symmetrical-collidine, PA1 sodium bicarbonate and PA1 pyridine,
Where according to the chain length, the letters alpha, beta, gamma and so on are given.
There are no chemical methods available at this time for the quantitative and selective oxidation of the primary hydroxyl functions of glucose-containing products such as polysaccharides and dextrins: In general, oxidation is partial or complete, producing many products and fragments. While the complete conversion of the primary hydroxyl functions of alpha- and beta-cyclodextrin can be accomplished by use of either catalytic oxidation (O.sub.2 /Pt) or nitrogen dioxide (N.sub.2 O.sub.4) treatments (Casu, B., Scovenna, G., Cifonelli, A. J. and Perlin, A. S., Carbohydrate Research, 63, 13, 1968), the application of equivalent techniques to polysaccharides results in the formation of either substantially depolymerized materials, or product mixtures containing both acid and aldehyde groups (Pigman, W. W., Browning, B. L., McPherson, W. H., Calkins, C. R. and Leaf, R. L., J. Am. Chem. Soc., 71, 2200, 1949). Secondary hydroxyl functions, however, are also oxidized to some extent, and nitrogen is incorporated in the form of nitrites or nitrates.
The nitrogen dioxide oxidation method can, for example, be employed for the preparation of heparin analogues derived from amylose, cellulose, guar gum and locust bean gum, for which C-6 oxidation yields of between 20-60% are obtainable but with depolymerization (Hoffman, J., Larm, O., Larsson, K., Andersoon, L. O., Holmer, E. and Soderstrom, G., Carbohydr. Polym., 2, 115-121, 1982). For cellulose the application of nitrogen dioxide in the gas phase or dissolved in carbon tetrachloride results in the predominant formation of D-glucuronic acid residues (Allen, T. C. and Cuculo, J. A., J. Polym. Sci., Macromol. Rev., 7, 189, 1973). Nitrogen dioxide treatment of bleached sulphate pulp introduces 0.7 mmol carboxyl residues per gram of cellulose; prolonged oxidation results in the formation of carbonyl functions and a severe reduction of the degree of polymerization (Luzakova, V., Marcincinova, T. and Blazej, A., Cell. Chem. Technol., 17, 227-235, 1983).
Another method for the preferential oxidation of primary hydroxyl functions involves the use of oxygen and Adams catalyst. This method introduces furanosyluronic and pyranosyluronic acid residues into polysaccharides. Treatment of rye-flour arabinoxylan and European larch arabinogalactan, two highly branched polysaccharides with oxygen, Adams catalyst and sodium hydrogen carbonate for 4 and 14 days, respectively, reportedly afforded the corresponding oxidized products containing 4% and 7.5% carboxyl functions (Aspinall, G. O. and Nicolson, A., J. Chem. Soc., 2503, 1960; Aspinall, G. O. and Cairncross, I. M., J. Chem. Soc., 3998, 1960). The unfavourably long reaction periods and low yields clearly limit the utility of this method. Similarly low yields are reported for the application of this catalytic oxidation method to 1,4-linked polysaccharides (Heyns, K. and Beck, M., cited as unpublished results in Heyns, K. and Paulson, H., Adv. Carbohydr. Chem. Biochem., 17, 194, 1962).
A patent disclosure by J. Hamuro (Japanese disclosure 75-54684, dated May 14, 1975) claims the preparation of polysaccharide polyaldehyde derivatives via the treatment of polysaccharide sulfonate or halogen derivatives with a sulfoxide or amine oxide. The process as described, requires the isolation and drying of the polysaccharide sulfonate intermediates prior to further derivatization. The subsequent modifications with dimethyl sulfoxide or pyridine-N-oxide were conducted at elevated temperatures (100.degree.-500.degree. C.) in the absence of any catalyst, and required reaction periods of 0.5-1.0 hours. The yields reported for the claimed polyaldehyde polysaccharide derivatives were very low, reaching degrees of substitution (DS) of only about 0.13. A closer examination of the claims made shows, however, the following points: the inventor claims infrared evidence (absorption at 1710-1700 cm.sup.-1) for the presence of the aldehyde functions combined with decreased absorptions (at 1602, 1360, 1170, and 810 cm.sup.-1) from which a degree of conversion into the polyaldehyde product of 70-90% is deducted. Whether any aldehyde functions introduced by the claimed process would be present, is questionable, in view of the well established fact, that aldehyde functions (introduced, for example, via periodate oxidation or similar means) of polysaccharides may undergo a series of inter- and intra-molecular condensation reactions in aqueous media (as are employed for the workup and isolation of the oxidized products) or upon drying. While the above-cited high conversion efficiencies of 70-90% are claimed on the one hand, the degree of aldehyde substitution is stated to be only 0.11, 0.13 and 0.20 for amylose, cellulose, and pachymaran derivatives, respectively, based on sodium borohydride reduction of the polyaldehydes.